1. Field of the Invention
The present invention relates to a conveyance apparatus for a processing step, as used in a conveyance line in which processing is carried out, such as a coating line or a machining line in a manufacturing plant.
2. Description of the Related Art
A prior art example of a conveyance apparatus with which a vehicle body is coated while being conveyed is disclosed in International Patent WO 02/053482. This conveyance apparatus is provided with a conveyance truck that is able to travel over immersion tanks, and pairs of swinging arms are provided on the conveyance truck, as two sets, at the front section and at the rear section of the truck in the direction of travel. Supporting bars are installed respectively between the free end sections of the pairs of swinging arms, and a vehicle body is supported on top of the front side supporting bar and the rear side supporting bar. By causing the front and rear side swinging arms to rotate downwards, in either an independent fashion or a mutually combined fashion, the vehicle body held on the supporting bars is caused to descend and is introduced into a coating material.
However, in the conveyance apparatus according to the prior art described above, the vehicle body is raised and lowered along an arc-shaped path of descent. Therefore, it is necessary to form an entrance to the immersion tank and an exit from the same, each of a large dimension, in the direction of travel of the conveyance truck. Moreover, if the vehicle body is to be lowered in a perpendicular vertical direction, it is necessary to move the conveyance truck in the direction of travel. Furthermore, if the direction of descent and ascent of the vehicle body is an arc-shaped direction, then a problem arises in that the positional control of the vehicle body and the control of the posture of the vehicle body become complicated, when it enters into the treatment liquid and when it exits from the same.